No abstract

No abstract

Density-functional theory is utilized to investigate the zero-temperature transition from a Fermi liquid to an inhomogeneous stripe, or Wigner crystal phase, predicted to occur in a one-component, spin-polarized, two-dimensional dipolar Fermi gas. Correlations are treated semi-exactly within the local-density approximation using an empirical fit to Quantum Monte Carlo data. We find that the inclusion of the nonlocal contribution to the Hartree-Fock energy is crucial for the onset of an instability to an inhomogeneous density distribution. Our density-functional theory supports a transition to both a one-dimensional stripe phase, and a triangular Wigner crystal. However, we find that there is an instability first to the stripe phase, followed by a transition to the Wigner crystal at higher coupling.

Impact shmr tests of the Kolsky Thin Hafer type vere used. to determine tho effect of temperature and strain-rate on the critical resolved shear stress for slip in aluminu..""n sin3le crystals at strain-rates of 10 4 scc-1 and in the temperature range 20°K to 500°K. The aluminum deformed in a .vi:..>cous•rnanner in that the flow stress was proportional to the plastic strain-rate. The behavior was found to be temperature dependent. The results were discussed in terms of dislocation damping models• I•:J:-.ere friction force acting on a dislocation results :Crom, at cryogenic temperatures, electronic viscosity, and at hig:O.cr temperatures, J;honon viscosity. The theories predicted general agreement as to the ::ncc:..:;:•i tude of the observed damping but some discrepancy was found to exist bet\.recn the observed and theoretical temperature dependence of tqe d~""npin~.